**Core Concept**
The Ligament of Cooper, also known as Cooper's ligament, is a fibrous structure used in surgical repair of femoral hernias. It serves as a reinforcing layer for hernia mesh placement in femoral hernia repair. The ligament is derived from the fascia lata and the iliopectineal line of the pelvis.

**Why the Correct Answer is Right**
Cooper's ligament is formed by the extension of the inguinal ligament, specifically the iliopubic tract, which is a fascial layer located between the iliopectineal line and the pubic bone. This ligament provides a strong, fibrous base for the repair of femoral hernias, allowing secure placement of the hernia mesh. The use of Cooper's ligament in femoral hernia repair is a technique developed by Sir Astley Cooper in the 18th century.

**Why Each Wrong Option is Incorrect**
**Option A:** The lacunar ligament is a different structure, also known as Gimbernat's ligament, which is a part of the inguinal ligament but not related to the formation of Cooper's ligament.

**Option B:** The pectineal line is a bony landmark on the pubic bone, but it is not directly related to the formation of Cooper's ligament.

**Option C:** The iliopubic tract is actually the correct answer, but since it is not listed, we will continue with the explanations for the other options.

**Clinical Pearl / High-Yield Fact**
When repairing femoral hernias, it is essential to identify Cooper's ligament as the key landmark for mesh placement. This technique reduces the risk of recurrence and provides a strong, long-lasting repair.

**Correct Answer: C.** Iliopubic tract.